The present invention concerns sterile collection and culturing of urine, and more particularly a sterile, disposable device for sterile collection and culture of urine in females.
Infections of the urinary tract are second in incience only to infections in the respiratory tract. Many females have been stigmatized with the misdiagnosis of being susceptible to frequent urinary tract infections as the result of the inaccuracy of present collection and culture methods. It is generally recognized that a high urinary bacterial count is indicative of significant bacterial infection, but when collecting a urine specimen, contaminating organisms or bacteria introduced initially in less than significant numbers can frequently lead to a problem, since urine is a good culture medium. Furthermore, a delay between the time of collection and microbiological examination of only 20 minutes, provides conditions for easy and ready bacterial growth which can result in erroneously high culture colony counts.
Based upon the foregoing, it has been recommended in the past that urine samples be innoculated within an hour after they are collected or be refrigerated immediately. It has also been suggested that a urine collection tube be coated on its inner surface with a culture-indicator medium which would provide a simple and reproducible method for screening of significant bacteria. Thus, this method would eliminate the step of transferring a urine specimen from the original container to a laboratory container, during which transfer additional contamination might occur. This method would yield more reliable results.
In a clinical study, it was found that patients do not receive adequate instruction on catching of a specimen and are often not motivated to provide a good "clean catch" specimen. This is a difficult problem in the female as vaginal discharge is frequently seen coincident with symptoms of urinary tract infection and is almost universally present in pregnant individuals. It is virtually impossible to collect a good clean catch specimen in the presence of significant vaginal discharge. This can result in a false positive culture rate, as high as 80 or 90% false. The following chart shows how this problem was reduced when a known catheter and collector arrangement was used versus an ordinary clean catch device:
______________________________________ Colonies Detected Clean Catch % Catheter Collection % ______________________________________ &gt;100,000 40.1% 5.8% Method failure 1 2% ______________________________________
Previous studies found method failures related to design of available culture devices that does not allow for assurance of adequate gas/air exchange to facilitate bacterial growth. This problem has been alleviated in the design of this device. 172 patients were tested and 40.1% of the patients had a positive clean catch culture versus only 5.8% positive in the catheter collection, where &gt;100,000 colonies is considered significant (positive). 22 patients in the clean catch group had multiple organisms and might not have been treated. Therefore, clean catch identified 27.3% of patients requiring therapy (over 100,000 colonies) versus 5.8% of catheterized tests showing the same need of therapy. If 100,000 colonies is considered the threshhold, more than four times the number of patients actually requiring therapy would have been given thereapy based on the clean catch results compared to the catheterized test results.
Even with the above stated improvements, however, there is still considerable opportunity for contamination of samples occasioned by the female anatomy and elevated bacterial colony counts due to delay in culturing the urine. It is therefore an object of the present invention to minimize these sources of error.
It is another object of the present invention to reduce contamination by reducing the number of containers used in taking specimens.
Catheterization has been thought to cause urinary tract infection, especially in pregnant patients. However, a study using a known catheter collecting system did not result in an increase in symptomatic urinary tract infections in pregnant individuals.
Furthermore, it is well known that asymptomatic bacteria in pregnancy may be associated with premature labor and a 50% risk of pyelonephritis. Many authors have recommended screening for bacteria in pregnant patients. Problems with present methods include cost, contamination, risk of inducing infection, personal time and perhaps most important, delay in initiating therapy. In one study, (Harris OBGYN,Vol. 53, pages 71-73) 28% of the cases of pyelonephritis occurred in a population of pregnant women screened for bacteria. These cases were theoretically preventable and were attributed to method failure. Greater than half of failures were related to a delay between collecting the urine specimen and being made aware of the culture results. My new system should prevent those failures, and results can be obtained in 24 hours. Thus, although testing is advised, the risk of taking contaminated samples reduces the value of the test results and often requires re-testing. A study looking at the cost effectiveness of this method of screening for urinary tract infection in pregnancy found a 61% cost savings over no screening method and greater than 52% saving over standard methods.